Screen plate for pulp press and the like



Sept. 6, 1966 1.. M. KOELSCH SCREEN PLATE FOR PULP PRESS AND THE LIKE Filed NOV. 30, 1964 INVENTOR. LESTER M (05 50/ ATTORNEYS United States Patent 3,270,663 SCREEN PLATE FOR PULP PRESS AND THE LIKE Lester M. Koelsch, Pittsfield, Mass., assignor, by mesne assignments, to Beloit Corporation, Beloit, Wis., a corporation of Wisconsin Filed Nov. 30, 1964, Ser. No. 414,521 7 Claims. (Cl. 100117) This invention relates to improvements in presses for continuously separating liquids from solids, such as pulp and the like.

In presses for the continuous dewatering of pulp and the like, and particularly pulp presses of the screw type, a generally conical spindle having helical flights extending therealong cooperates with a liner screen to exert pressure on the pulp and extract moisture therefrom and deliver a relatively dry cake of pulp.

In such presses, the liner screen is backed up by a heavy screen plate perforated throughout, with holes larger in diameter than the holes in the screen. The liner screen is then attached to the screen plate by screws or welding. It is extremely diflicult to attach the liner screen to the screen plate and due to this difliculty in attaching the liner screen to the screen plate, it is impossible to obtain perfect contact between the liner screen and screen plate, with the result that the liner screen will deflect during a squeezing and dewatering operation, resulting in frequent failures of the screen, making it necessary to frequently remove and replace the entire liner screen. Replacing the liner screen besides taking the press out of operation is an expensive and time consum ing operation.

A principal object of the present invention, therefore, is to remedy these deficiencies in pulp dewatering presses by eliminating the liner screen and placing removable screens in the perforations in the screen plate with the perforated portions of the screens on the inside of the screen plate.

Another object of the invention is to improve upon the screw press pulp or slurry dewaterers heretofore in use by eliminating the liner screen and providing individual screen inserts in the perforations of the backing screen plate.

A still further object of the invention is to provide an improved form of pulp dewaterer having a novel and improved form of screen plate having individual screen inserts mounted in the wall thereof and thereby simplifying the construction of press screen and enabling screens of different hole sizes to be readily assembled to the screen plate.

A still further object of the invention is to provide an improved form of pulp dewaterer of the screw press type in which a screen plate extends about the tapered pressing spindle of the press and individual screen inserts having perforations of selected hole sizes are mounted in the perforations of the backing screen from the inside thereof.

These and other objects of the invention will appear from time to time as the following specification proceeds and with reference to the accompanying drawings wherein:

FIGURE 1 is a view in side elevation of a screw type dewatering press constructed in accordance with the principles of the present invention with certain parts of the housing for the press and the screen plate broken away, in order to illustrate certain features of the invention;

FIGURE 2 is a fragmentary sectional view illustrating one form of screen insert that may be inserted in the perforations of the backing screen plate;

FIGURE 3 is a view somewhat similar to FIGURE 2 but illustrating another form of screen insert construct- 3,27%,663 Patented Sept. 6, 1966 ed in accordance with the principles of the present invention;

FIGURE 4 is a view somewhat similar to FIGURES 2 and 3 but illustrating still another form of screen insert constructed in accordance with the principles of the present invention; and

FIGURES 5 and 6 are end views of screen inserts such as shown in FIGURES 2, 3 and 4, showing the screen inserts perforated with different hole sizes.

In the embodiments of the invention illustrated in the drawing, I have shown in FIGURE 1 a screw type of pulp dewatering press, including a generally cylindrical casing or housing 10 having an inlet 11 entering said housing through the top of said housing and in axial alignment with the axial center line of said housing, and a water outlet 12 leading from the wall of said housing, at the bottom of a screw or spindle 13.

The screw or spindle 13 is suitably journalled in said housing at its ends coaxial with the axial center of said housing and is rotatably driven by power and diverges from its upper to its lower end in the uniform taper. The screw 13 has a plurality of flights 15 extending helically therealong. The helix angle of the flights 15 on the upper portion of the spindle is shown as being relatively steep and decreases as the flights are spaced downwardly along the spindle, and is relatively flat at the lower end of said spindle. The flights 15 are shown as being arranged with a double lead, and for each flight on said spindle there is another flight on the other side of said spindle, with its center spaced from the center of the opposite flight, to provide balance during rotation of said spindle.

The spindle 13 is shown as being encased in a screen plate 16, herein shown as being cylindrical in form, of substantially the inside diameter of the outside diameter of the flights 15. The screen 16 may be a relatively heavy plate having a plurality of perforations 17 therein throughout the periphery of said spindle.

As the pulp slurry enters the inlet 11 and during rotation of the spindle 13 the pulp will be compressed by the flights with an equal and opposite compression force exerted on each flight while the water will flow through the perforations 17 to be discharged through the outlet 12. The spacing of the flights to provide a balanced flight exactly 180 opposite from each flight, besides exerting an equal and opposite compressive force on each flight, forces the pulp or other material being dewatered uniformly through the press with no offset load on the spindle that may tend to create a wobble or unbalanced condition of the spindle.

The relatively high helix angle in the upper portion of the spindle enables the relatively high moisture content material to be moved very rapidly for the extraction of the free moisture therefrom and as the moisture is re moved from the material, the helix angle of the flights lowers and moves the material downwardly at a slower rate, at the same time the distance from the spindle body to the screen decreases. More pressure is thus exerted on the pulp toward the lower end of the spindle as the need for extracting moisture from the pulp increases, it being understood that the dewatered pulp is discharged from the spindle at the lower end thereof into a pulp basin (not shown) into which the pulp may drop by gravity and be discharged from the press in a conventional manner.

Referring now in particular to the screen 16 and several novel features of the invention, in FIGURE 2 the holes or perforations 17 in the screen are shown as being cylindrical and as having enlarged diameter inner end portions opening toward the inside of the screen and forming shouldered recesses 19, for screen inserts 20 in the form of buttons mounted in said perforations from the inside of the screen. The screen inserts or buttons 20 have perforated caps 21 facing the spindle 13 and having a plurality of uniformly spaced perforations 22 leading therethrough. The perforations 22 may be of various sizes dependent upon the requirements for the particular material being dewatered, as shown in FIG- URES and 6. The cap 21 of the button 20, shown in FIGURE 2, terminates into a shouldered undersurface 23 extending inwardly from the margin thereof and seated on the shoulder of the shouldered recess 19. The shouldered undersurface 23 terminates into a collar 24 having an outer cylindrical wall portion 25, fitting within the perforation 17.

The perforated cap 21 of the button 20 forms a rigid drain area approximately flush with the inner surface of the screen plate 13 and prevents tramp material passing through the press, from damaging the large areas of the screen holes or perforations 17.

Where one or more screen inserts or buttons 2i may be damaged by tramp material, they may readily be replaced without necessitating the replacement of the entire liner screen. It should also be noted that the perforations of the inserts may be varied from the top to the bottom of the screen for certain dewatering conditions, and relatively large diameter perforations may be provided at the top of the screen while smaller diameter perforations may be provided at the bottom of the screen and vice versa where conditions require.

In the form of the invention illustrated in FIGURE 3, I have shown a screen plate 16 having frusto-conical perforations 17a leading therethrough from the inside thereof and have shown screen inserts in the form of perforated buttons 20a, having frusto-conical collars 24a leading inwardly therefrom, of the taper of the perforations 17a and fitting within said perforations. These buttons being subjected to pressure from the inside are firmly held in position, but may readily be removed from the outside when damaged or where it may be desired to change the hole sizes of the buttons.

In the form of the invention illustrated in FIGURE 4, I have shown perforations 1712 leading through a screen plate 16 of uniform diameter through their length and have shown a screen insert or button 2% having an integrally formed cylindrical collar 26, which may be pressed into the perforation 17b.

In all three forms of the invention illustrated in FIG- URES 2, 3 and 4, the buttons may readily be removed and may be of the same size throughout the press. Thus, the conventional liner screen has been replaced by a series of detachable screen inserts, mounted in the perforations of the backing screen from the inside thereof, and closely adjacent said screen, to form a rigid drain area.

While I have herein shown and described several forms in which the invention may be embodied, it may readily be understood that various variations and modifications in the invention may be attained without departing from the spirit and scope of the novel concepts thereof.

I claim as my invention:

1. In a screen particularly adapted for dewatering presses,

a screen plate in the form of a relatively thick walled cylinder having an inner peripheral wall and having a plurality of relatively large diameter perforations leading radially through the wall thereof, uniformly spaced throughout the area of said screen plate,

a plurality of relatively thin walled screen inserts inserted in said perforations from the inner peripheral wall of said cylinder,

each screen insert having a thin walled convex face extending inwardly of the inner peripheral wall of said cylinder having a plurality of uniformly spaced perforations leading therethrough and having a collar extending from said face fitting with-in a respective perforation in said screen plate from the inside thereof and positioning said convex face to extend inwardly of the inner peripheral wall of said screen plate.

2. A screen in accordance with claim 1,

wherein the perforations in the screen plate have shouldered entering inner end portions opening through said inner peripheral wall,

and wherein the screen inserts are in the form of buttons having perforated convex faces terminating into shoulders extending radially inwardly of the margins of the faces and seated on said inner shouldered end portions of the screen plate perforations, and positioning the convex faces of said buttons to extend inwardly of the screen plate.

3. A screen in accordance with claim 1,

wherein the perforations in th screen plate are frustoconical and converge in diameter from the inner peripheral wall to the outside of the screen plate,

and wherein the screen inserts are in the form of buttons having convex faces having a plurality of uniformly spaced perforations leading therethrough and having frusto-coni-cal collars extending inwardly of said convex faces and fitting within said frusto-conical perforations from the insides thereof to retain the inserts thereto with the convex faces thereof extending inwardly of the inner wall of the screen plate.

4. A screen in accordance with claim 1,

wherein the perforations in the screen plate have uniform diameter cylindrical wall portions,

and wherein the screen inserts are in the form of buttons having perforated convex faces extending inwardly of the inner peripheral wall of the screen plate and having cylindrical collars extending therefrom, retained to the uniform diameter wall portions of said screen plate by pressing engagement of said collars with the perforations of said screen plate and positioning the convex faces to extend inwardly of the inner peripheral wall of the screen plate.

5. In a screen press adapted to dewater slurries of pulp and the like,

a housing having an inlet leading thereinto at its upper end, coaxial with the vertical center thereof, and having a discharge outlet leading from the wall thereof, spaced downwardly from said inlet,

a vertically extending spindle journa-lled in said housing in axial alignment with said inlet and having a frustoconical Wall increasing in diameter from the upper to the lower end of said spindle and having spaced helical flights extending therealong,

the helix angle of which flights decreases from the upper to the lower end of said splndle,

a relatively thick walled cylindrical screen extending about said spindle and flights and having a uniform diameter inner peripheral wall portion having uniformly spaced uniform perforations extending radially therethrough throughout the area thereof and opening to said flights,

and individual screen inserts for said perforations having relatively thin walled perforated convex face portions extending inwardly of the inside of the inner peripheral wall portion of said screen plate and having collars extending inwardly of said convex faces,

engaging the walls of the perforations of said screen plate and positioning said convex faces to extend inwardly of said screen plate.

6. A screen press in accordance with claim 5,

wherein the perforations in the screen plate are relatively large diameter perforations and have cylindrical wall portions terminating at the interior wall of the screen plate into shouldered portions facing radially inwardly of the screen plate and forming seats for said screen inserts and positioning said convex faces to extend inwardly of the inner peripheral wall of said screen plate and retaining said screen inserts to said screen plate by the pressure of the fiow of water therethrough from the inside to the outside of said screen plate.

7. A screen press in accordance with claim 5,

wherein the perforations in the screen plate have frustoconical Walls decreasing in diameter from the inside to the outside of said screen plate,

and wherein the screen inserts have frusto-conical collars extending inwardly from the convex faces thereof, fitting within the frusto-conical perforations of said screen plate and positioned thereby to position said convex faces to extend inwardly of the inner Wall of said screen plate.

References Cited by the Examiner UNITED STATES PATENTS 874,418 12/1907 McEvoy t 210498 X 1,045,355 11/1912 Zander 100127 1,288,864 12/ 1918 Fowler 1001 17 X 2,709,957 6/ 1955 Armstrong 100-117 FOREIGN PATENTS 459,222 8/ 1949 Canada.

743,181 1/ 1933 France.

LOUIS O. MAASSEL, Primary Examiner. 

1. IN A SCREEN PARTICULARLY ADAPTED FOR DEWATERING PRESSES, A SCREEN PLATE IN THE FORM OF A RELATIVELY THICK WALLED CYLINDER HAVING AN INNER PERIPHERAL WALL AND HAVING A PLURALITY OF RELATIVELY LARGE DIAMETER PERFORATIONS LEADING RADIALLY THROUGH THE WALL THEREOF, UNIFORMLY SPACED THROUGHOUT THE AREA OF SAID SCREEN PLATE, A PLURALITY OF RELATIVELY THIN WALLED SCREEN INSERTS INSERTED IN SAID PERFORATIONS FROM THE INNER PERIPHERAL WALL OF SAID CYLINDER, EACH SCREEN INSERT HAVING A THIN WALLED CONVEX FACE EXTENDING INWARDLY OF THE INNER PERIPHERAL WALL OF SAID CYLINDER HAVING A PLURALITY OF UNIFORMLY SPACED PERFORATIONS LEADING THERETHROUGH AND HAVING A COLLAR EXTENDING FROM SAID FACE FITTING WITHIN A RESPECTIVE PERFORATION IN SAID SCREEN PLATE FROM THE INSIDE THEREOF AND POSITIONING SAID CONVEX FACE TO EXTEND INWARDLY OF THE INNER PERIPHERAL WALL OF SAID SCREEN PLATE. 